OCR 21 st Century Science from 2011 B2 - Keeping Healthy

1. OCR 21st Century Sciencefrom 2011 B2 - Keeping Healthy Learning about: Vaccinations, disease and resistance. Antibiotics and drug testing Heart disease Keeping a healthy balance Revision F5 to start

2. Contents Page – B2 Keeping Healthy OCR 21st Century • Disease and Resistance • Antibiotics and drug testing • Heart disease • Keeping a healthy balance • B2 OCR (Biology A) Past Paper Questions ^ Please click on a topic you would like to revise about / or please click HERE to start all the topics starting from Disease and Resistance

3. Disease and ResistanceClick HERE to go back to the contents page OR click to start this topic.

4. What causes disease and infections? What is the first line of defence in our body? The first line of defence in our body is our skin. Just imagine how our body would be without our skin, in fact you can just think now that if you had a paper cut without your skin you could get a serious infection. Another natural defence system is your stomach acid. Your stomach contains hydrochloric acid which simply removes any harmful bacteria as soon as you start to digest your food and drink. Bacteria zoomed in on a hand Hydrochloric acid symbol

5. Pathogens – Bacteria, Fungi, Viruses • Pathogens is a scientific term which basically represents all micro-organisms that cause harm in the human body. You should be well aware of Bacteria, Fungi and Viruses. * Bacteria are one of the most common type of harmful micro-organisms that cause us infections and make us feel ill. In size, they’re very small yet they can multiply millions of times and release poisonous toxins to make us feel very ill. * Fungi is probably the least common micro-organism but it can still cause great harm. It is present on moulds and mushrooms and can cause stomach poisoning if digested. * Viruses are several times smaller than bacteria, in fact they’re known as one of the smallest organisms ever known. They have a protein coat which consists of the DNA. Viruses can only produce in host cells, once inside they produce hundreds of copies of themselves making the host cell damaged and eventually making it burst. This then allows the virus to travel in the bloodstream and take over different cells in the body.

6. Growth of Micro-organisms • The most dangerous part of harmful bacteria, fungi or viruses is when they reproduce. • They can reproduce asexually ( making clones) and they reproduce rapidly causing harm to your body within a short length of time. • Micro-organisms need warm, soft, moist conditions with plenty of oxygen, the ideal place is the human body, that’s why they duplicate so fast. You can see that there is 1 bacterium duplicating itself every 20 minutes, each bacterium divides itself in to 2, so when there is 100 bacterium, in the next 20 minutes there will be 200. Question: If a bacterium reproduces Itself every 30 minutes How much will there be In 2 hours?

7. White Blood Cells • As well as natural defence systems ( passive immunity) like skin, chemicals in tears, chemicals in sweat and stomach acid, there is also white blood cells. White blood cells are the second triggered defence systems in our body it’s called ‘’ active immunity’’ and the white blood cells prevent pathogens from getting any further into the body by using a variety of methods. • White blood cells can either: Engulf and digest the pathogen, they can bind and neutralise the pathogen by releasing antitoxins, or they can directly attack the pathogen by releasing antibodies.

8. Memory cells and mutations • The process of white blood cells doesn’t just end there. Memory cells are a great advantage to the body because they keep in mind which foreign harmful micro-organisms entered the body and make sure that antibodies are produced at a faster rate next time. So if you do get re-infected with that same disease you will probably be immune because your body would have destroyed it without you getting ill.

9. Memory cells and mutations • Mutations are the complete opposite, mutations can happen in micro-organisms once they enter your body. Some micro-organisms that have a higher mutation rate will result in their DNA constantly changing so you won’t be immune to that disease/infection because your body won’t recognize it and again it will take a longer time to become immune to it. This frequently happens in viruses, that’s why it is hard to create a vaccine that destroys viruses because by the time the DNA has changed the new vaccine won’t have even been developed. ^ Cat with different eye alleles, mutations caused in her eyes

10. Types of white blood cells • There are 2 main groups of white blood cells, the first is Phagocytes and the 2nd is Lymphocytes. • Phagocytes: These white blood cells can move through the blood vessels and move closer to the skin layer where they can easily get rid of the bacteria by either ingest and engulf or release an enzyme that will destroy them. Once the phagocyte has absorbed the pathogen it can send out messages to lymphocytes. • Lymphocytes help by identifying the specific antibody needed for that micro-organism. Once they meet a certain antigen that matches with them, they quickly reproduce themselves and release a lot of antibodies to get rid of that micro-organism. • Together they destroy the harmful micro-organisms.

11. Antibiotics and drug testingClick HERE to go back to the contents page OR click to start this topic.

12. Antibiotics and drug testing • Vaccination is a safe form of a dangerous disease which gives you immunity to that specific disease. • Vaccinations have helped clear many deadly diseases, the benefits of having a vaccines outdraws the side effects to it. • Vaccination is one of the key things that keep you and your country safe from a epidemic. • A vaccination can be given to you in many forms for example: it could be a live pathogen treated to make it harmless, it could be a dead pathogen, it could be the toxins released by the pathogen and it could be a harmless fragment of the pathogen. Either way the pathogen goes inside your body and white blood cells identify it and destroy it, in the future antibodies will be released more quickly and destroy the harmful bacteria before you get ill.

13. Vaccines and boosters • It is important to understand when a harmful disease could mutate, that’s why vaccines like the MMR vaccine and the anti-tetanus vaccine are repeated every 10 years so that the immune system’s memory doesn’t weaken and if you do get infected with the disease again the immune system will still have good memory and release the antibodies needed. • Side effects: The side effect of vaccines can be a mild fever as vaccines are not 100% safe and can cause small side effects, it is important to consider that whilst developing a vaccine you have to take into account that the side effects of the vaccine won’t be more dangerous than actually the immunity that you will get from the vaccine. You have to consider how much people are infected and how much people of a population it could be passed on to. You have to also consider that is actually treating the person with medicines cheaper than creating a vaccine?

14. Antibiotic and resistance • You might have heard of Natural selection, most of the time it helps us and gives us an advantage but when it comes to bacteria mutating, natural selection is probably the thing happening. Mutations is a big problem because vaccines need to be redeveloped and it can will cause no effect to your body if the micro-organisms have mutated! An example of this is MRSA – this is resistant to most type of antibiotics. • So, to slow down the process of bacteria becoming resistant we should always complete a full course of antibiotics and not take antibiotics for minor problems. • This is the process that shows bacteria becoming resistant: • 1.) Random changes or mutations occur on the proteins which are on the surface of the cells in the genes of bacterial cells. • 2.) Some mutations protect the bacterial cell from the effects of the antibiotic • 3.) Bacteria without the mutation die or cannot reproduce with the antibiotic present, this is an example of natural selection. • 4.) The resistant bacteria are able to reproduce and create colonies of their resistant bacteria.

15. Testing drugs • New medical drugs are first tested before they’re prescribed and sold, these are the stages: • 1.) First a sample of the medicine is tested on cells in a laboratory kept in certain conditions. • 2.) If this works then it is tested on animals and the animals are carefully monitored to watch out for side effects. • 3.) If this is all successful then the medicines take part in clinical trials where healthy human volunteers try them – and if them tests are successful then they try it on the patients who actually need it.

16. Human Trials - part 1 A human trial is a process where a new medication has successfully passed the examination on cells in the laboratory and on animals. The next process is trying it on humans. There are 2 groups, one is called the test group and one is called the control group. The test group are a group of healthy volunteers who are given the real drug. The control group are people who have been given the existing treatment or a placebo if there is no existing treatment, the placebo is a fake replacement of that drug. The reason why this happens is because scientists need to compare the results to check for effectiveness and this process is known to be reliable and safe.

17. Human Trials - part 2 • There are 3 main types of clinical trials, blind, double blind and open label: • Blind: The researchers know what group the volunteers are put in but the volunteers do not know. • Double blind: Neither the volunteers nor the researchers know which drug has been given to which group. • Open label: Both the doctor and patient know which drug has been given, this sort of thing happens when a patient has a disease that is incurable and the doctors believe they won’t recover from their diagnosed illness. • Placebo: Some doctors think that giving a placebo to a patient is totally unfair because they know that the patient will not recover from the drug and their is also false hope given to the patient.

18. Heart DiseaseClick HERE to go back to the contents page OR click to start this topic.

19. Heart Disease • The heart is a muscle and it requires it’s own blood supply from the coronary arteries because of the nutrients and O2 it needs and for the waste products to be removed. The heart is sometimes referred as a double pump because it pumps blood from the arteries, and expects blood from the veins. • Unfortunately genetic and lifestyle factors can affect your BP and so in result, this affects how well your heart works. Having a lifestyle full of fat and salt can cause plaques to build up in your coronary arteries and block the flow of the blood meaning that your heart will not receive enough nutrients to function properly, this causes red blood cells to permanently die and this increases your chance of a heart attack. The circulatory system consists of your heart, which pumps blood. The capillaries which diffuse essential nutrients and oxygen as there are only one cell thick and the capillaries are close to your body cells. The veins which pump blood to the heart with low pressure and valves. The arteries which pump blood from the heart with high pressure.

20. Veins, Capillaries, Arteries The veins have thin layers of muscle wall and elastic fibres. They have a small lumen as the blood pressure is low whilst flowing to the heart and they have valves to stop the blood flow going in the opposite direction. Capillaries are essential because they allow food and oxygen to diffuse through to other cells whilst the waste is diffused from the cells. Capillaries walls are only one cell thick. The arteries have thick layers of muscle, elastic fibres and thick outer walls with a large lumen. The blood flows at a high pressure from the heart so it is important no leaks are occurred.

21. Measuring your heart rate • Monitoring your heart is vital especially if you have heart disease. Your heart is made to work faster if you have any clots forming because of fatty foods and a poor diet. This means that when your BP is measured, it comes as HIGH BP. Low BP can also be a concern because not enough blood could be getting to your heart, so the best place to be is in between. Because every body is different scientists have created a chart which helps you see how your BP is getting on. The higher rate is when your heart is contracting and the lower rate is when your heart is relaxing. • Ways to check your BP: • Measure your pulse rate for a minute • Use a BP machine • In fact, BP does not measure your heart beating but it measures the blood pressure on the arteries whilst the blood is flowing from the heart.

22. Heart attacks • Heart attacks happen because of the coronaries arteries getting blocked, this is due to genetic and lifestyle factors such as: • Alcohol Misuse • Eating foods high in salt and fat • No exercise • Stress • Smoking • How do they happen? • When you eat foods high in fat and carbohydrates and do no, or little exercise, clots can start forming on the coronary arteries. The coronary arteries can’t burn the fat of because of no exercise so they have to put with it. Unfortunately if your lifestyle carries on like this, a blood clot can form which means little or no blood is pumping through the body, this causes a heart attack because your heart cells start to die.

23. Epidemiological studies • Epidemiological studies are studies carried out by scientists over a large population. Normally the scientists are trying to find a cause for a correlation. • For example, scientists may be trying to find out if smoking is the main factor that causes heart disease so it would be wrong to try to get people to smoke BUT since there are thousands of people who smoke already, studies on them can give scientists a better insight. • These studies last a long time so scientists can get reliable results.

24. Results from scientists must be replicated • If a scientist comes up with a claim for example ‘’ smoking increases the risk of heart disease’’ then it should be replicated by other scientists and checked for any errors that may have occurred. These scientists that are checking the claim must be critics and try to find the errors because if the claim is wrong/misleading then it can cause for example; medicines that are developing that could potentially unblock clots in the arteries – stop their research because this theory might not match with what they’re researching on.

25. Keeping a healthy balanceClick HERE to go back to the contents page OR click to start this topic.

26. Keeping a healthy balance • Maintaining a constant internal environment in your body is called homeostasis. Homeostasis is vital because it keeps our body cells functioning properly. • Homeostasis keeps: • 1.) Our internal body temperature at 37 degrees • 2.) Keeps our water levels balanced.

27. Control systems in our body • Imagine you’re at home in front of a warm fire - suddenly you have to go outside in a snowy blizzard to get your shopping. • Your body temperature will start to decrease but your receptors on your skin will detect the stimuli and send impulses to the processing centres and the processing centres will produce responses to try and keep your temperature balanced to 37 degrees. • If it gets too cold, you’re body can get hypothermia, which can be fatal. • Another example is a premature baby in a incubator, the incubator will automatically switch the heater on if the temperature goes below 37 degrees ( body temp) and it will automatically switch off if the temperature goes above 37 degrees ( body temp). This is keeping balanced and maintaining homeostasis.

28. Negative feedback • Negative feedback ensures that everything is reversed to it’s set level. Negative feedback controls temperature, blood oxygen levels and salt levels. • So, if our salt levels rise, negative feedback will send a impulse to make sure that the salt levels are returned to normal, this normally involves something happening in your body to maintain a steady balance.

29. Maintaining water balance: The kidneys maintain our water balance by the blood plasma. If the concentration of the blood plasma is high then less water is re-absorbed from the kidneys meaning our urine becomes more dilute, if the concentration of the blood plasma is low them more water is re-absorbed from the kidneys and our urine becomes concentrated. This maintains the water level. Factors such as external temperature, exercise, salt level, fluid intake can all depend on the level of water in the blood plasma. Water balance • Our kidneys maintain: • Water levels in blood plasma • Urea • Salt levels • Any of these substances that are not put back into the blood plasma are excreted. • Our bodies take in water from food and drink and respiration. • Our bodies lose water when we sweat, urinate, faeces and when we breathe out on a cold day because the water condenses into water vapour. Drugs that affect our water balance: Alcohol decreases ADH production meaning less water is re-absorbed from our kidneys making them more dilute. Ecstasy increases ADH production meaning more water is re-absorbed from our kidneys making our urine concentrated. Read on about ADH on the next page

30. ADH – Anti Diuretic Hormone • ADH is a great example of Negative feedback. ADH is a chemical which is released by the pituitary gland in the Brain (Hypothalamus). • If the receptors detect that the water levels in the blood plasma are high then less ADH is released which makes the kidneys re-absorb less water which makes your urine dilute and the water levels get back to normal. • If the receptors detect that the water levels in the blood plasma are low then more ADH is released which makes the kidneys re-absorb more water which makes your urine more concentrated but the water levels get back to normal. • Alcohol decreases ADH production meaning less water is re-absorbed from our kidneys making them more dilute. This can cause dehydration in your body because of the loss of water which results in unbalanced water levels. • Ecstasy increases ADH production meaning more water is re-absorbed from our kidneys making our urine concentrated. This can cause too much water in your body and this can result cells not functioning properly.

31. B2 OCR ( Biology A) Past paper QuestionsClick HERE to go back to the contents page OR click to start this topic.

32. B2 OCR ( Biology A) Past paper Questions:

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